For these questions I'd contact BMW via the contact methods listing at the end of the letter.
Originally Posted by tol4o
I am 50/50 on doing this recall
Is there an expiration date? Can I do it later if a problem shows up?
What I gathered from the letter was that the car might be producing too high of NOX levels and if it is then some of the emissions components will prematurely go bad and cause an SES light eventually. So their solution to this is to replace those parts now and do some programming on the car as well to compensate for the new parts differences.
I think it would be hard to judge impressions after this recall at this point in time. If it in fact has a reflash of the ECU then people will have to deal with that ECU <-> Driver learning period and the car should in fact seem different during that.I'd find someone who gets it around now then ask them of their impressions in a few months.